Snow plows on plow vehicles such as pickup trucks, dump trucks and the cause the plow vehicle to suffer a cooling problem. The issue is not the weight nor the drag of the plow but rather the airflow disruption engendered by the snow plow.
To illustrate this problem, FIG. 1 shows a side view of a plow vehicle 10 with a plow 12 and ancillary mounting equipment 14. However, it is apparent from viewing this side view that air flow is massively disrupted from its normal straight flow. As the vehicle 10 moves under normal circumstances, it is designed to generate a largely unimpeded airflow to radiator 16. With a curved blade 12 in front of the radiator 16, however, the air flow is disrupted and is scooped up by the upper edge and body of the blade 12, generating a high pressure area CH in front of the blade 12 in the exact same manner in which the snow on the ground is scooped up by the lower edge and body. Plow blades may be commonly seen with a vortex of snow swirling around in the front of the blade, which eventually exits via one side (one end) of the horizontal blade. What is not visible to the naked eye is the fact that the air flow follows the same path, being entrained by the blade and snow in the high pressure area CH and carried around the end of the plow blade 12.
A limited amount of air passes over the plow blade 12 as shown by arrow CA'. This air from above the plow is pulled by a low pressure area ‘L’ behind the blade downward, thus resulting in a very small flow past radiator 16. However, this small flow exists in the partial vacuum ‘L’ generated by the blade 12. Since the vehicle radiator 16 is not designed for use in a partial vacuum, the real world result is that the vehicle engine begins to overheat in the midst of snow, forcing the operator to periodically stop and cool the engine or causing a significant loss of power.
This is not a theoretical issue. The overheating problem caused by the plow acting like a scoop to move air away from radiators has been long noted by plow operators and the reason for this understood. The problem, therefore, is of considerable vintage.
A search in the United States Patent Office Collection reveals previous attempts to solve this problem. U.S. Pat. Nos. 5,544,434 to Calvachio, Jr. and 4,587,750 to Larson teach airfoils or scoops which attempt to solve this problem. Testing these types of units reveals immediate flaws. In particular, the mountings of these devices are wildly inadequate to the battering received by snow plows. Real world snow plow blades are driven across rugged uneven surfaces and they may frequently encounter small but immovable obstacles which are completely hidden by the snow. An object as insignificant as a pebble embedded in a tarmac road surface can actually bring a plow vehicle to a halt, and more typical hidden obstacles include concrete gutters, sidewalks, curbs and the like. Most plows do not come to halt under such conditions, though, because the plow blades are normally hinged so that they can rotate when encountering a small object, with strong springs urging the plow blade back to normal position after the object is passed.
The battering, vibration and shaking the plow blade undergoes makes a mockery of the light mountings taught by the 1 434 and 750 references. As mentioned, testing showed that light mountings made to the rib 102 very quickly shake themselves free from the blade and vanish into the snow in front of the plow or under the wheels of the vehicle.
These mountings have other problems besides lack of durability. They do not allow easy height adjustments of the device for differing combinations of plows and vehicles. This is important to effectiveness: if an airfoil cannot be adjusted in height to gather the required amount of air and redirect it towards the radiator, then the device does not prevent the overheating / power loss problems seen by operators. A single height setting cannot provide this as plow vehicles come in a wide range of heights and radiators are variously disposed at various heights as well. Plows also come in a variety of heights and a variety of lengths of separation from the front of the vehicle. Finally the shapes of the plows results in differing degrees of vortex formation, and if an airfoil is not located at a location which receives a strong airflow, that is, if the air foil is located in the low pressure zone even though it is atop the blade, then the air foil in the low pressure zone cannot function in any event. The combinations of plows and vehicles means that the air foil must be adjustable not just in angle but also in height.
In addition, these devices do not easily fit to plows lacking such an upper rib, having an upper rib inappropriate for the mounting, or split V-blade plows.
These references teach two simple air foil shapes: a true air foil and a flat scoop. Thus, these devices are not found widely distributed among plow operators. In addition to the ‘434 patent to Calvachio, Jr. and the 750 to Larson, trunking or duct works have been tried to solve this problem. Examples of this include U.S. Pat. Nos. 5,881,479 to Pavey and 4,896,915 to Morandi et al. These patents do not disclose airfoils which ride above the plow blade but rather scoops which redirect a certain amount of the incoming air more closely toward the radiator. It is difficult to see how such trunking devices could possibly be made adjustable in height, particularly as imagination is required to guess the details of the mountings of these two devices. Some of these devices are too far forward to properly direct air to the vehicle radiator area. Others, such as the ‘915 device, have weak mounts, become clogged with snow, and reduce the effective turning radius of the plow vehicle by impinging into the area between the plow and the vehicle when the come close together during turns.
Finally, there are numerous deflectors which are designed to deflect snow which spills over the top of the plow blade and direct it downward actually away from the plow vehicle. (Abstract, U.S. Pat. No. 5,309,653 to Pease et al. and Col. 1, line 21, U.S. Pat. No. 3,432,947 to Peitl). Since these devices have a different function and result it seems safe to dismiss them and their kin as irrelevant to devices which try to direct air *toward* the plow vehicle: reference prior art cannot violate its own fundamental operation.